Immigration was a hot topic throughout the EU referendum campaign.
Photograph: REX/Shutterstock

European Union citizens will be free to come to the UK for several years after Brexit despite repeated promises from leave campaigners that restrictions would be swiftly introduced, a Whitehall thinktank has found.

A report released on Thursday by the Institute for Government (IfG) warns ministers it will be “unfeasible” to create a new immigration system by April 2019 at the end of the two-year deadline when Britain plans to leave the EU.

An end to EU immigration was a major concern among leave voters and forms a key part of Theresa May’s negotiating priorities. During the referendum campaign, David Davis – now Brexit secretary – said Britain must end its “disastrous” immigration policy.

The scale of the administrative challenge is too great and the current immigration system should be kept until a replacement is ready to avoid disruptive changes to labour markets, the think tank has concluded.

It also found the current process for registering EU nationals was “not fit for purpose” and the Home Office could require up to 5,000 extra civil servants to cope with large numbers of applications and appeals.

Jill Rutter, the institute’s Brexit programme director, said: “The political imperative for change in immigration is significant, but so is the administrative challenge. The scale of the task – creating a new immigration system – is huge and it is critical that government gets it right.

“The current process for dealing with permanent residence applications from EU nationals is not fit for purpose, as the government itself acknowledged. It needs to be streamlined as a matter of urgency and as a first step towards a new post-Brexit system.”

Under article 50, any country that invokes the provision has two years to negotiate a settlement before it leaves. The treaty clause has never been used before and legal and political opinions are split on how exactly secession would take place.

Freedom of movement is one of the four pledges enshrined in the Treaty of the European Union, giving citizens of member states the right to move freely within the EU to seek work.

Thursday’s report points out that the scale of the task makes successful implementation of a new immigration regime by April 2019 unfeasible for the government, employers, landlords and providers of public services who rely on the system and support its functioning.

Joe Owen, the IfG’s researcher and report author, said: “Brexit is an opportunity to design an immigration system that is more effective for the country and less burdensome for employers.

“It’s important that the government avoids making multiple changes and introducing unnecessary disruption and confusion.

“To provide stability, we should continue with the existing migration system until the new one is ready.”

Business leaders urged the government to stand firm rather than create a raft of new rules, which would be “a bureaucratic nightmare” for firms.

Séamus Nevin, head of employment and skills policy at the Institute of Directors, said: “What employers don’t want is the instability of having to waste a great deal of time and effort learning to navigate multiple rounds of changes and new rules. That would create a bureaucratic nightmare for recruiters, especially smaller firms.

“If something’s worth doing it’s worth doing right, so if that means continuing with current arrangements for a period of a few years until the Home Office can put the infrastructure in place to implement a new system, then it will be worth the wait.”